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The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. Every health condition can be assigned to a unique category and given a code, up to six characters long. Such categories can include a set of similar diseases.

The International Classification of Diseases is published by the World Health Organization. The ICD is used world-wide for morbidity and mortality statistics, reimbursement systems and automated decision support in medicine. This system is designed to promote international comparability in the collection, processing, classification, and presentation of these statistics. The ICD is a core classification of the WHO Family of International Classifications (WHO-FIC).

An important alternative to the mental disorders section of the ICD is the American Psychiatric Association's (APA) Diagnostic and Statistical Manual of Mental Disorders (DSM), which is the primary diagnostic system for psychiatric and psychological disorders within the United States and some other countries, and is used as an adjunct diagnostic system in other countries. Since the 1990s, the APA and WHO have worked to bring the DSM and the relevant sections of ICD into concordance, but some differences remain.

The ICD is revised periodically and is currently in its tenth edition. The ICD-10, as it is therefore known, was developed in 1992 to track mortality statistics. ICD-11 is planned for 2011 and will be revised using Web 2.0 principles.[1] Annual minor updates and three yearly major updates are published by WHO. The ICD is part of a "family" of guides that can be used to complement each other, including also the International Classification of Functioning, Disability and Health which focuses on the domains of functioning (disability) associated with health conditions, from both medical and social perspectives.



In 1893, a French physician, Jacques Bertillon, introduced the Bertillon Classification of Causes of Death at the International Statistical Institute in Chicago. A number of countries adopted Dr. Bertillon’s system, and in 1898, the American Public Health Association (APHA) recommended that the registrars of Canada, Mexico, and the United States also adopt it. The APHA also recommended revising the system every ten years to ensure the system remained current with medical practice advances. As a result, the first international conference to revise the International Classification of Causes of Death convened in 1900; with revisions occurring every ten years thereafter. At that time the classification system was contained in one book, which included an Alphabetic Index as well as a Tabular List. The book was small compared with current coding texts.

The revisions that followed contained minor changes, until the sixth revision of the classification system. With the sixth revision, the classification system expanded to two volumes. The sixth revision included morbidity and mortality conditions, and its title was modified to reflect the changes: Manual of International Statistical Classification of Diseases, Injuries and Causes of Death (ICD). Prior to the sixth revision, responsibility for ICD revisions fell to the Mixed Commission, a group composed of representatives from the International Statistical Institute and the Health Organization of the League of Nations. In 1948, the World Health Organization (WHO) assumed responsibility for preparing and publishing the revisions to the ICD every ten years. WHO sponsored the seventh and eighth revisions in 1957 and 1968, respectively.

In 1959, the U.S. Public Health Service published The International Classification of Diseases, Adapted for Indexing of Hospital Records and Operation Classification (ICDA). It was completed in 1962 and a revision of this adaptation – considered to be the seventh revision of ICD – expanded a number of areas to more completely meet the indexing needs of hospitals. The U.S. Public Health Service later published the Eighth Revision, International Classification of Diseases, Adapted for Use in the United States. Commonly referred to as ICDA-8, this classification system fulfilled its purpose to code diagnostic and operative procedural data for official morbidity and mortality statistics in the United States.


The ICD-9 was published by the WHO in 1977. At this time, the U.S. National Center for Health Statistics created an extension of it so the system could be used to capture more morbidity data and a section of procedure codes was added [1]. This extension was called "ICD-9-CM", with the CM standing for "Clinical Modification".

ICD-9 consists of two or three volumes:

  • Volumes 1 and 2 contain diagnosis codes. (Volume 1 is a tabular listing, and volume 2 is an index.) Extended for ICD-9-CM
  • Volume 3 contains procedure codes. ICD-9-CM only

According to the World Health Organization Department of Knowledge Management and Sharing, the WHO no longer publishes or distributes the ICD-9 which is now public domain.[citation needed]


See also: List of ICD-9 codes

The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) is based on the World Health Organization's Ninth Revision, International Classification of Diseases (ICD-9). ICD-9-CM is the official system of assigning codes to diagnoses and procedures associated with hospital utilization in the United States.

The National Center for Health Statistics (NCHS) and the Centers for Medicare and Medicaid Services are the U.S. governmental agencies responsible for overseeing all changes and modifications to the ICD-9-CM.


Main article: List of ICD-10 codes

Work on ICD-10 began in 1983 and was completed in 1992 [2].)

Adoption was relatively swift in most of the world, but not in the United States. Since 1988, the USA had required ICD-9-CM codes for Medicare and Medicaid claims, and most of the rest of the American medical industry followed suit.

On 1 January 1999 the ICD-10 (without clinical extensions) was adopted for reporting mortality, but ICD-9-CM was still used for morbidity. Meanwhile, NCHS received permission from the WHO to create a clinical modification of the ICD-10, and has produced drafts of the following two systems:

  • ICD-10-CM, for diagnosis codes, is intended to replace volumes 1 and 2. A draft was completed in 2003.
  • ICD-10-PCS, for procedure codes, is intended to replace volume 3. A final draft was completed in 2000.

However, neither of these systems is currently in place. There is not yet an anticipated implementation date to phase out the use of ICD-9-CM. There will be a two year implementation window once the final notice to implement has been published in the Federal Register. [3]. A detailed timeline is provided here.

Other countries have created their own extensions to ICD-10. For example, Australia introduced their first edition of "ICD-10-AM" in 1998, and Canada introduced "ICD-10-CA" in 2000.


The first draft of the ICD-11 system is expected in 2008, with publication following by 2011 and in 2013+ implementation will take place. WHO has announced that it will apply Web 2.0 principles for the first time to revise the ICD. The ICD revision process will be open to all comers willing to register, back their suggestions with evidence from medical literature and participate in online debate over proposed changes.[2]

Current use

ICD has become the most widely used statistical classification system in the world. Although some countries found ICD sufficient for hospital indexing purposes, many others felt that it did not provide adequate detail for diagnostic indexing. The original revisions of ICD also did not provide procedure codes for classification of operative or diagnostic procedures. As a result, interested persons in the United States began to develop their own adaptation of ICD for use in the United States.

Hospitals and other healthcare facilities index healthcare data by referring and adhering to a classification system published by the U.S. Department of Health and Human Services: International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM). The Clinical Modification or CM system was developed and implemented in order to better describe the clinical picture of the patient. The CM codes are more precise than those needed only for statistical groupings and trend analysis. The diagnosis component of ICD-9-CM is completely consistent with ICD-9 codes.

Note that ICD-10 was adopted in 1999 for reporting mortality, but the ICD-9-CM remains the data standard for reporting morbidity. Revisions of the ICD-10 have progressed to incorporate both clinical code (ICD-10-CM) and procedure code (ICD-10-PCS) with the revisions completed in 2003. However, ICD-9 has not been phased out by the new revision.

Public data reporting

Mental and behavioral disorders

As well as general medical diseases, the ICD includes a section classifying mental and behavioral disorders. This has developed alongside the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders and the two manuals seek to use the same codes. There are significant differences, however, such as the ICD including personality disorders on the same axis as other mental disorders, unlike the DSM. The WHO is revising their classifications in these section as part the development of the ICD-11 (scheduled for 2014), and an "International Advisory Group" has been established to guide this[4].


The years for which causes of death in the United States have been classified by each revision as follows:

  • ICD-1 - 1900
  • ICD-2 - 1910
  • ICD-3 - 1921
  • ICD-4 - 1930
  • ICD-5 - 1939
  • ICD-6 - 1949
  • ICD-7 - 1958
  • ICD-8A - 1968
  • ICD-9 - 1979
  • ICD-10 - 1999

See also


  1. ^
  2. ^

Official ICD-9

  • ICD-9-CM Official homepage at the CDC

Look up codes

  • database at Stanford University
  • Free 2008 ICD-9-CM database
  • ICD-9-CM search - Search and navigate ICD-9-CM

Official ICD-10

Look up codes

Conversion between ICD-9-CM-A and ICD-10-AM

  • Excel spreadsheets with ICD-10-AM to ICD-9-CM-A and vice versa at
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "ICD". A list of authors is available in Wikipedia.
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